Comprehension of PrEP Efficacy Estimates
Varying operational understandings of efficacy rates from trials (e.g., 92% efficacy for all users vs. 100% efficacy for 92% of users). PrEP failures due to user behavior or unique physiological features.
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Reactions to PrEP Efficacy Estimates from Clinical Trials
92% efficacy (iPrEx trial among MSM with detectable drug levels) was acceptable. Lower efficacy estimates (e.g. 44%) often unacceptable given side effects and cost. PrEP was acceptable at several lower boundaries of efficacy, ranging from 50% to 100%.
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Development of Personal Effectiveness Expectations
Generalized estimates of efficacy do not apply to all PrEP users due to behavioral and biological differences. Many expected personal effectiveness of 90–100% due to high predicted adherence, low predicted risk behaviors, “average” physiology. Others said they could not use efficacy estimates from clinical trials to predict their own personal effectiveness.
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Numerical Information versus Paraphrases
Most preferred percentage-based information for credibility, ease of comprehension, ease of comparison, and as proof of scientific basis. Some preferred paraphrases to improve understanding and limit concern about failure. Offering both message types will ensure that messages reach a diverse audience.
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Ranges versus Point Estimates for Communicating Efficacy
Most preferred hearing a full range of efficacy for completeness and as a warning against poor adherence. Others were deterred by ranges because lower-bound efficacy estimates reduced acceptability, multiple percentages may be confusing, and ranges may encourage excessive dosing to get “extra” effectiveness.
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Success-Framed versus Failure-Framed Messages
Many preferred success-framed messages for increased optimism, comprehension, and easier comparisons. Others preferred both message frames, particularly during clinical consultation, for increased message credibility and strengthening of adherence and condom use motivations. A few participants preferred failure-framed messages.
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Suggestions for Tailoring Efficacy Messages to Users
Visual aids and multimedia are needed to communicate efficacy to individuals who are not skilled with percentages. Different message framing strategies may be needed for different stages of PrEP use (e.g., initial consultation vs. ongoing use).
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